The present invention relates to a negative working light-sensitive composition, and particularly to a light-sensitive composition which is suitably used in a photosensitive lithographic printing plate having excellent developability in aqueous alkali developers, excellent printing durability and excellent film strength in image areas during development. The present invention also relates to a photosensitive lithographic printing plate having the novel light-sensitive composition applied thereto.
The vast majority of light-sensitive substances used for imparting light sensitivity to negative-forming printing materials are diazonium compounds. The most commonly used are diazonium resins, of which the condensation product of p-diazdiphenylamine and formaldehyde is representative.
The composition of the light-sensitive layers of photosensitive lithographic printing plates using diazo resins can be classified into two groups: (1) those containing diazo resins is without binders, as in U.S. Pat. No. 2,714,066, and (2) those containing mixtures of diazo resins and binders as in Japanese Unexamined Patent Publication (hereinafter Kokai) No. Sho 50-30604(=U.S. Pat. No. 4,275,138). However, in recent years, most light-sensitive lithographic printing plates using diazonium compounds have come to use diazonium compounds and polymer binders in order to impart high printing durability.
Such light-sensitive layers, as described in U.S. Pat. No. 4,123,276, can be of the so-called alkali developing type in which the unexposed areas are removed by means of an aqueous alkali developer, or of the so-called solvent developing type in which the unexposed areas are removed by an organic solvent type developer. However, from the viewpoint of labor health and safety, alkali developing types are given attention. Binders for use in such alkali developing type light-sensitive layers can be copolymers of 2-hydroxyethyl (meth)acrylate and carboxylic acid-containing monomers such as methacrylic acid as disclosed in the above-mentioned U.S. Pat. No. 4,123,276; copolymers of aromatic hydroxy group-containing monomers and carboxylic acid-containing monomers such as methacrylic acid as described in Japanese Kokai No. Sho 57-43890; polymers made by reacting the carboxylic acid portion formed by the reaction of the remaining OH groups of polyvinyl acetal resin and an acid anhydride with a halogenated compound having a hydroxy group or an amino group as described in U.S. Pat. No. 4,741,985; or polymers made by reacting sulfonyl isocyanate with a polymer having free OH groups as disclosed in Japanese Kokai No. Sho 47- 9902 (=U.S. Pat. No. 3,732,105). However, none of the above binders are sufficiently satisfactory.
Japanese Kokai No. Sho 63-113450 (=U.S. Pat. No. 4,877,711) discloses a polyurethane resin having a substituent group with an acidic hydrogen, which represents a great improvement in abrasion resistance, but much further improvements are desirable.
In U.S. Pat. No. 3,404,003, a diazonium compound-containing light-sensitive composition layer is proposed having an organic phosphonate other than polyvinyl phosphonate. However, this type of layer does not have the resin of high abrasion resistance as used in the present invention and therefore can not be expected to have sufficient effectiveness.